Late Side Effects

Some early side-effects described above can persist for years, although their nature and impact will likely change over time. Other late side-effects may only develop after many years however. These often result from the damage caused to blood vessels during radiation treatment of the original cancer. Because blood vessels nourish nerves, muscles and bones, if nourishment is prevented, then these tissues gradually alter and even decay over time. It is always important to follow up any changes in your body with your doctor or oncologist, no matter how long after the original treatment, as late-side effects can themselves pose serious threats to your health and well being.  

Dry mouth (xerostomia)

If you still experience xerostomia (or dry mouth) for more than two years, then the damage to your salivary glands are likely to be permanent. While early side-effects focussed on difficulties in eating and drinking, late side effects include long-term damage to your teeth through poor oral hygiene, which can lead to the onset of osteoradionecrosis - see below.  Xerostomia may also lead to burning mouth syndrome, a burning sensation that can affect anywhere in the mouth including throat, tongues, gums, lips, palate. 

If burning mouth syndrome occurs, temporary relief can be found through eating and drinking. For longer term solutions, avoidance of certain types of food and drink may be necessary (such as spicy food and alcohol), and taking tobacco. Like management for tinnitus, cognitive behaviour therapy might be suitable for some people. 


Radiation-induced fibrosis usually occurs within months after treatment has finished, and can take many years to develop fully. Fibrosis is the excessive formation of fibrous connective tissue, a result of radiation damage to tissues, that can occur in muscles, skin, subcutaneous tissues, organs and even bones. It results in the stiffening over time of muscles and joints, and can lead to severe mobility issues. For head and neck cancer patients, this may result in stiff neck and shoulders, and trismus (the inability to open the jaw very wide). Fibrosis may also occur over time in the throat, making swallowing difficult, as those muscles become tighter.

While radiation-induced fibrosis cannot be stopped, its effects can be countered through doing daily exercises for life, such as stretching the neck muscles, rolling the head clockwise and anticlockwise, shoulder shrugs and rolls, and jaw stretching exercises to name but a few. A type of massage called myofascial release can also help. If fibrosis affects your ability to swallow, then see your doctor for a referral to a speech and language therapist.


Trismus is the inability to open the jaw fully to eat  or drink. It is a side-effect of radiation damage to muscle fibres in the jaw, causing fibrosis (see above). As well as eating and drinking, chewing, oral care, and speech and language can be impacted as well.

Your speech and language  therapists will provide you with simple exercise regimes to use during and after treatment to help reduce this side effect, e.g. jaw stretching exercises. It is recommended you do these as a prophylactic to reduce any future impact that trismus may have.


Osteoradionecrosis is a late complication of radiotherapy that is difficult to treat and yet common in patients having gone through radiotherapy as part of their cancer treatment. Radiotherapy treatment can impair the body’s ability to maintain a blood supply to the jaw giving rise to osteoradionecrosis. It is associated with necrosis (death) of the jawbone and often results in severe pain, pus formation (within the mouth and through the face), and breakdown of the overlying tissues. Deterioration in dental health after radiation therapy can also lead to osteoradionecrosis. Unchecked, osteoradionecrosis can be life-threatening. 

Before you undergo radiation treatment, a dentist will assess how healthy your teeth and gums are, and will recommend extraction of any unhealthy teeth. This dental prophylaxis is partly done to minimise the risk of future osteoradionecrosis. Once you are able to brush your teeth again, maintain excellent oral hygiene. Use an ultra-high fluoride toothpaste (5 mg of fluorine) such as Duraphat, use a high-fluoride mouth-wash, and visit your dentist regularly. 

Chemotherapy induced peripheral neuropathy (CIPN)

CIPN can be permanent if it hasn’t disappeared after 6-9 months. For example, tinnitus and changes in sensation in hands and feet. Parts of your face and neck may also feel numb to touch or movement as well. 


Radiation treatment to the head and neck can cause hypothyroidism in many patients, because the radiation damages the thyroid gland in the lower neck, affecting its ability to produce hormones critical in regulating the body’s growth and metabolism. Side effects include physical and mental sluggishness, leading to weight gain, fatigue, dry hair and skin, hair loss, constipation, memory decline and depression. The extent of effects on people are however very varied.

Ensure you have annual blood checks to check on both thyroid stimulating hormone (TSH) and thyroxine (a type of thyroid hormone also known as free T4) levels. If levels of these hormones are lower than normal then you may have hypothyroidism, and you may be prescribed a thyroid hormone replacement.

Attention, thinking and memory problems

Changes to attention, thinking and memory can be grouped under cognitive impairments, and can be caused by both chemotherapy and radiotherapy. Cognitive impairments can also result from other medications taken to help early- and late-effect side-effects of cancer treatment. Brain fog is real! 

Cognitive impairments can be managed through medication and cognitive rehabilitation and training, such as exercises to improve memory and problem solving. Learning a new language works really well as a cognitive rehabilitation tool. Exercise, including gentle walking, gardening, swimming etc, also has important physical and cognitive benefits.

Early Side-Effects

Side-effects experienced during treatment and in the months just after treatment, sometimes called the recovery period

Late Side-Effects

Side-effects that may occur from one year to many years in the future after treatment. Descriptions, patient reflections and recommendations